Niacin Flush: Causes, Symptoms, and Management

Niacin is a water-soluble form of vitamin B3 found in dietary supplements. Healthcare providers also prescribe higher dosages of niacin to manage cholesterol levels. Though niacin has considerable health benefits, taking high amounts can cause side effects, including niacin flush.

Niacin flush occurs when the skin on the face, arms, or chest turns red and becomes itchy or uncomfortable. It arises as niacin in the bloodstream triggers an immune response. This causes blood vessels in the outer layers of the skin to dilate, increasing blood flow.

Attacks typically resolve within a half hour, making this condition more unpleasant than dangerous. However, very high levels of niacin can damage the liver and affect vision, among other symptoms. It’s important to understand what niacin does, how it can affect you, and what you can do to manage niacin flush.    

Niacin, or vitamin B3, plays a critical role in metabolism, or the chemical process of absorbing and using energy from food. Tissues in the body convert niacin into active forms that help to transfer energy from carbohydrates, fatty acids, and cholesterol to the cells. These also have an antioxidant function, neutralizing free radicals and reactive oxygen species (ROS), which are damaging compounds that can build up in the body.    

Primarily, healthcare providers recommend or prescribe niacin to help manage unhealthy cholesterol levels, known as dyslipidemia. High doses of niacin lower triglycerides and low-density lipoprotein (LDL) cholesterol—”bad” cholesterol—and raise high-density lipoprotein (HDL), or “good” cholesterol. This helps prevent cardiovascular conditions like:

• Heart disease
• Heart failure
• Atherosclerosis (buildup of fats, cholesterol, and other substances in and on the artery walls).

Boosting niacin also has an anti-inflammatory effect. This means it reduces inflammation—the body’s immune response—triggered by infections or diseases. In a study of people who were hospitalized with acute non-ST-elevation acute coronary syndrome (NSTE-ACS), a heart condition that causes chest pains, researchers found supplements of niacin safely lowered inflammation levels.  

Niacin supplements or prescriptions can also treat niacin deficiency, which is when you don’t have enough vitamin B3. This leads to a condition called pellagra, characterized by a sunburn-like discolored red or brown rash on skin exposed to sunlight. Pellagra may also cause a bright red tongue, nausea or vomiting, and fatigue, among other symptoms. However, niacin deficiency is often caused by malnutrition and is rare.

The flushed, red skin and the other symptoms of niacin flush arise as blood fills in small, dilated subcutaneous vessels in the skin just below the surface. Excess niacin in the bloodstream activates Langerhans cells in the skin, which regulate immune function. These cells trigger the release of prostaglandins, chemicals that cause blood vessels to open up.

It takes 30-50 milligrams (mg) of niacin to trigger this response, so it’s mainly a concern with high-dose supplements and prescribed forms. The risk is also higher if you take supplements or medications on an empty stomach.

Your tolerance to niacin may also make you more sensitive to niacin flush. Consider starting niacin supplements with smaller doses and gradually increasing. 

Niacin flush sets on about a half hour after taking niacin, with the symptoms lasting about 60 minutes before resolving on their own. Individual cases of niacin flush can vary, with typical signs of niacin flush including:

• Skin redness that’s similar to blushing, typically in the face, arms, or upper chest
• Warmer skin in affected areas
• Itchy skin
• Tingling or burning sensation anywhere in your upper body

Largely, healthcare providers consider this condition an unpleasant side-effect rather than a dangerous health condition. However, niacin flush may be accompanied by other symptoms, like headache, rash, dizziness, and low blood pressure. Very high doses of niacin can cause diarrhea, nausea, and jaundice, a yellowing of the skin and eyes due to liver damage.

Though it causes some of the same skin symptoms—like redness and itchiness—a niacin flush is not an allergic reaction. Allergic reactions are immune responses triggered by exposure to certain foods, pet dander, pollen, plants, insect bites, and medications. Allergy symptoms affect the skin and other body parts. Common signs of allergies include:

• Hives, welts, and swelling in the skin
• Itchiness
• Nasal congestion and difficulty breathing
• Cough, wheezing
• Rash, patches of discolored skin
• Red or watery eyes
• Diarrhea
• Flushing in the face, redness
• Nausea and vomiting
• Heart palpitations
• Swelling in the face, eyes, or tongue

Very severe allergic reactions cause anaphylactic shock, a medical emergency that can become fatal. Get emergency help if you experience severe symptoms like facial swelling, difficulty swallowing, wheezing, and loss of consciousness.

While a niacin flush can be very uncomfortable, it doesn’t damage your body. The feeling should pass on its own within a couple of hours, and it doesn’t require medical treatment. People who use niacin regularly can also develop a tolerance to it over time. As they do, they become less prone to its side effects, including niacin flush.

While niacin flush is a relatively harmless side effect, very high doses of niacin can profoundly affect the body. Since the liver processes vitamins, doses of 1,000-3,000 mg of niacin daily—used to treat high cholesterol—can cause liver damage and failure. This high dose may also lead to dangerously low blood pressure, vision problems, and other harmful effects.

Managing niacin flush may involve treating the symptoms and changing niacin intake to stop the reaction. Methods that may help include:

• Changing niacin type: There are different types of niacin, with nicotinic acid and nicotinamide (or niacinamide) being the most common types found in supplements. Nicotinic acid helps with hyperlipidemia (high blood lipid levels), but nicotinamide does not. Nicotinamide is less likely to cause skin flushing and negative health effects.
• Using extended-release niacin: Supplements and medications with niacin can be fast-acting or have a longer release. Because they work more gradually, extended-release types are less likely to cause niacin flushing, and when they do, it’s less severe.
• Scaling up: If you’re taking therapeutic niacin for cholesterol, consider starting with a smaller dose for some time before moving up to larger amounts. This way, you can develop a better tolerance for this therapy.
• Taking aspirin: Aspirin blocks the prostaglandin activity, which manages niacin flush. Typically, providers recommend doses of 325 mg aspirin about 30 minutes before taking niacin.
• Taking it with food: Taking your supplements with meals and on a full stomach slows down how quickly your body absorbs the niacin. This helps prevent flushing symptoms.
• Eating apples: Apple pectin, a kind of plant fiber, can help manage niacin flushing. Researchers found this effect comparable to that of aspirin for this condition.

Niacin flush is a wave of redness and warmth in the face, chest, or arms after taking high levels of the B vitamin, niacin. Found in dietary supplements and available in very high, prescription-strength doses, niacin helps to manage high cholesterol.

Too much niacin in the blood, such as from taking high doses, triggers an immune reaction. In addition to facial flushing, this condition can cause itching, burning, and tingling in the skin.

Though unpleasant, a niacin flush isn’t a dangerous condition and rarely requires treatment. The symptoms are temporary, typically resolving on their own within a couple of hours. Some methods to manage this condition include adjusting your niacin intake and taking aspirin.